Paul Moore, the 50-year-old HBOS whistleblower, is relishing the limelight.

And why not.

His nine-page submission to the Treasury Select Committee, published last week, has proved incendiary, enabling the former head of risk at the Scottish bank to exact the sweetest revenge on the man who sacked him from HBOS in 2005, Sir James Crosby.

A former barrister, Moore put the skills he learnt at the bar to good effect, with a testimony that forced the surprising resignation of Sir James from his role as deputy chairman of the Financial Services Authority (FSA) on Wednesday.

Moore's claims, first made in a BBC documentary aired in the autumn of last year, but largely ignored until last week, are explosive.

He remains resolutely confident in the assertions he made in 2005, in spite of a statement from the City regulator rubbishing those claims.

The FSA commissioned the Square Mile bean-counter KPMG to scrutinise Moore's claims at the time, eventually concluding that they were without merit. But that KPMG was HBOS's official auditor and was in effect investigating its own work when looking at Moore's claims has left a whiff of unease.

Even though KPMG failed to find any smoking gun on the back of Moore's claims, the FSA was clearly worried about the HBOS train careering out of control. Its own routine investigations into the bank, known as Arrow reviews, yielded more potential red flags than normal. And that the FSA asked HBOS to put aside a greater level of risk capital in 2004, one year prior to Moore's claims, suggests the bods at Canary Wharf felt something could be awry at HBOS.

In his submission to the select committee, released last week, Moore paints a staggering picture of a bank out of control, growing at breakneck speed with little in the way of checks and balances.

"I told the board they ought to slow down ... I told them that their sales culture was significantly out of balance ... I certainly knew the bank was going too fast, had a cultural indisposition to challenge and was a serious risk to financial stability and consumer protection."

He portrays HBOS as a bank built on the old-boy network, where friendships rather than financial acumen or talent counted for much.

"Charles Dunstone [the Carphone Warehouse founder who was once a non-executive director at HBOS] admitted to me one day words to the effect that he had no real idea how to chair the retail risk-control committee. He admitted to me he was very friendly with [HBOS chief executive] Andy Hornby and they met quite often socially."

Unlike the telecoms tycoon Dunstone, Moore has clocked up plenty of miles in the financial services arena.

After hanging up his law-court robes, he became a partner at KPMG in 1995, where he stayed until 2002.

After his three-year stint at HBOS, which ended in a tribunal and a settlement with the bank, Moore was hired by Marsh, the insurance giant. He spent just nine months in the role of head of compliance for Europe and the Middle East. No reason has been given for his sharp exit.

After leaving Marsh, Moore founded his own telecoms firm, Complete Networks, a Yorkshire-based company of which he is now non-executive chairman. Filings at Companies House show Complete Networks posted a deficit of £13,750 for the year to the end of November 2007.

Moore is also a director at Xt3 Media, a Catholic social-networking firm that, on its website, promises to "evangelise [the Catholic faith] through all media streams".